Gas sensing properties of a two-dimensional graphene/h-BN multi-heterostructure toward H2O, NH3 and NO2: A first principles study

Two dimensional nanomaterials are promising for gas sensing applications due to their large surface to volume ratio. Recent studies show that the sensitivity of pristine graphene, the most prominent two-dimensional ma-terial, can be improved by several methods such as doping, decoration and combination with other two-dimensional materials. In the present work a two-dimensional graphene/h-BN multi-heterostructure, in the form of G/h-BN/G/h-BN/G, is proposed for gas sensing applications, which is expected to outperform pristine graphene devices. The adsorption energies and charge transfer for H2O, NH3 and NO2 molecules are investigated at the density functional level of theory. The presence of two insulating h-BN layers induces potential barriers for charge carriers and changes the current mechanism to the quantum tunneling regime, which is highly sensitive to the modulation of the potential barrier due to the adsorbed molecules. A first principles method based on non-equilibrium Green's function formalism is employed for the calculation of the device current in various envi-ronments. The proposed device shows little sensitivity toward H2O but it is very sensitive toward NH3 and NO2. Moreover, NO2 adsorption increases the device current, while NH3 adsorption reduces the current, a property which can result in a selective sensing of these two gas molecules.